Demand response implemented in an infrastructure having a dc link

ABSTRACT

A system for regulating electrical energy transfer over a pathway including a DC link ( 16, 18, 20 ) is provided. The system is configured for computing a rate of electrical energy flow through the DC link at least in part on a basis of a state of balance between power generation and a load determined from frequency measurement ( 32, 34 ) and for adjusting the rate of electrical energy flow through the DC link. An electrical vehicle charger is provided that includes a power input for connection to an AC power distribution network and a power output for connection to an electric vehicle, and is configured for determining a rate of electrical energy flow through the power output by using as a factor a state of balance between power generation and load in an AC power distribution network to which the power input connects. A method for regulating electrical energy transfer over a pathway including a DC link is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 62/111,807 filed on Feb. 4, 2015, the contents of whichis hereby incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to systems, devices and methods for performingdemand response in an electric power delivery infrastructure having a DClink.

BACKGROUND

Electric power delivery infrastructures exist that are inherently ACbased but involve some sort of DC link. An example is the DCinterconnect between two AC power distribution networks. The DC linkallows a power transfer between the two AC power distribution networkswhile allowing each AC power distribution network to maintain its ownphase and frequency characteristics.

The DC link has a rectifier stage to convert the incoming AC electricalenergy in DC electrical energy and an inverter stage that converts theDC electrical energy back into AC electrical energy. The conversion ofAC to DC is independent of the phase and the frequency in either ACpower distribution network at any given moment. However, the conversionDC to AC needs to take into account the phase and frequency of the ACpower distribution network that receives the electrical energy such thatthe energy injection is properly synchronized. The synchronization isperformed by a controller that samples the phase and frequency of thereceiving AC power distribution network and operates the inverter stageto generate an AC waveform that has the same frequency and phase as thereceiving power distribution network.

The DC link can be bi-directional allowing the electrical energytransfer to be reversed. In this instance, each stage of the DC link canselectively operate as a rectifier stage and as an inverter stage. Thecontroller is configured to sample the phase and frequency in bothnetworks and uses the relevant phase/frequency information depending onthe direction of the electrical energy transfer.

Another example of a power delivery infrastructure using a DC link is anelectric vehicle charging station. The charging station receives ACelectrical energy that is converted to DC and supplied in DC form tocharge the battery of the vehicle. The rate at which the electricalenergy is delivered to the electric vehicle is controlled to suit theneeds of the charging process. A control module on the vehicledetermines the rate at which the electrical energy needs to be deliveredto the battery and communicates with the charging station that regulatesit accordingly. The regulation is performed by changing the DC voltage;the lower the DC voltage supplied, the lower the rate at which theelectrical energy is supplied. Conversely, the higher the DC voltage,the higher the rate of energy delivery.

Demand response refers to a dynamic response that the demand, i.e., theentity that receives the electrical energy manifests, based on certainconditions in the AC power distribution network that supplies theelectrical energy. One example of response is to reduce the consumptionof electrical energy when the AC power distribution network experiencesa power generation deficit. Another example is to increase theconsumption of electrical energy when the AC power distribution networkexperiences a power generation excess. Examples of demand responsestrategies are described in PCT International Publication No. WO2013/177689 A1 the contents of which is hereby incorporated by referenceherein.

SUMMARY

In accordance with a broad aspect, a system for regulating electricalenergy transfer over a pathway including a DC link is provided. Thesystem includes a data processing device, which includes a machinereadable storage encoded with non-transitory software for execution by aCPU, the software being configured for computing a rate of electricalenergy flow through the DC link at least in part on a basis of a stateof balance between power generation and load in an AC power distributionnetwork to which the pathway connects and an output for generating acontrol signal for adjusting the rate of electrical energy flow throughthe DC link according to the computed rate.

In accordance with another broad aspect, an electrical vehicle chargeris provided. The electrical vehicle charger includes a power input forconnection to an AC power distribution network, a power output forconnection to an electric vehicle to supply electrical energy forcharging a battery of the electric vehicle and a data processing device.The data processing device includes a machine readable storage encodedwith non-transitory software for execution by a CPU, the software beingconfigured for determining a rate of electrical energy flow through thepower output by using as a factor a state of balance between powergeneration and load in an AC power distribution network to which thepower input connects and an output for generating a message to acontroller of the electrical vehicle to notify the controller that therate of electrical energy flow is being adjusted on the basis of a lossof balance between power generation and load in the AC powerdistribution network.

In accordance with yet another broad aspect, an electrical vehiclecharger is provided. The electrical vehicle charger includes a powerinput for connection to an AC power distribution network and a poweroutput for connection to an electric vehicle to supply electrical energyfor charging a battery of the electric vehicle. The electrical vehiclecharger also includes a data processing device, including a machinereadable storage encoded with non-transitory software for execution by aCPU, the software being configured for determining a rate of electricalenergy flow through the power output by using as a factor a state ofbalance between power generation and load in an AC power distributionnetwork to which the power input connects. The data processing device isconfigured to negotiate with an electrical controller of the electricvehicle a rate of charge to be supplied to the electrical vehicle when aloss of balance occurs between power generation and load in the AC powerdistribution network.

In accordance with a further broad aspect, a method for regulatingelectrical energy transfer over a pathway including a DC link isprovided. The method includes computing a rate of electrical energy flowthrough the DC link at least in part on a basis of a state of balancebetween power generation and load in an AC power distribution network towhich the pathway connects and adjusting the rate of electrical energyflow through the DC link according to the computed rate.

These and other aspects of the invention will now become apparent tothose of ordinary skill in the art upon review of the followingdescription of embodiments of the invention in conjunction with theaccompanying drawings.

DESCRIPTION OF THE DRAWINGS

A detailed description of embodiments of the invention is providedbelow, by way of example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a diagram illustrating two AC power distribution networksconnected by a DC link;

FIG. 2 is a more detailed diagram of the DC link shown in FIG. 1;

FIG. 3 is a flowchart illustrating the decisional process implemented bythe software controlling the operation of the DC link shown in FIGS. 1and 2;

FIG. 4 is a diagram of another example of implementation of theinvention, illustrating an electric vehicle charging station to which isconnected an electric vehicle and which has a battery that is charged bythe charging station;

FIG. 5 is a more detailed diagram of the vehicle charging station shownin FIG. 4;

FIG. 6 is a flowchart illustrating the decisional process implemented bythe software controlling the operation of the vehicle charging stationshown in FIGS. 4 and 5;

FIG. 7 is a flowchart illustrating the decisional process implemented bythe software controlling the charging of the electric vehicle; and

FIG. 8 is a diagram of a DC link according to another embodiment of theinvention, providing logging functions to account for electricitytransfer between two networks and also recording occurrence ofextraneous events such as under frequency conditions in either network.

It is to be expressly understood that the description and drawings areonly for the purpose of illustrating certain embodiments of theinvention and are an aid for understanding. They are not intended to bea definition of the limits of the invention.

DETAILED EXAMPLE OF IMPLEMENTATION

FIG. 1 illustrates two AC power distribution networks, namely network 1and network 2 designated by reference numerals 10 and 12, respectively,connected to each other by a DC link 14. The purpose of the DC link 14is to allow electric energy to be transferred from one network to theother while allowing each network to operate at its own phase andfrequency. This way, there is no need to synchronize the networks sothey operate at the same phase and frequency. In most instances, thefrequency of the electrical energy in both networks will be the same,however the phase will be likely different.

A more detailed block diagram of the DC link is shown in FIG. 2. The DClink has three identical DC channels 16, 18 and 20. Each DC channelhandles a single electrical energy phase. Since the electrical energy isdistributed in each network by a three-phase AC power stream, one DCchannel handles each phase separately.

Since the DC channels 16, 18 and 20 are identical in terms of structureand operate in the same manner, only one will be described forsimplicity.

The DC channel 16 has a rectifier/inverter stage 22 that is connected toanother rectifier/inverter stage 24 via a DC connection 26. Therectifier/inverter stages 22, 24 operate as rectifier or inverterdepending on the direction of power flow. For example, if network 10 issending electrical energy to network 12, the rectifier/inverter stage 22operates as a rectifier while the rectifier/inverter stage 24 operatesas an inverter. If the power flow direction was to be reversed, therectifier/inverter stages 22, 24 would operate in the reverseconfiguration.

Note that, for an electrical energy flow that is set once and will notchange, a simpler DC channel structure can be used that has a dedicatedrectifier stage connected to the source network and a dedicated inverterstage connected to the receiving network.

The rectifier stage 22 operates by converting the incoming electricalenergy on a given phase from AC to DC. For example, the rectifier stage22 may use a solid state rectifier bridge that provides full-waverectification. The output of the rectifier stage 22 is a rectifiedelectrical energy flow, which for convenience is referred to in thisspecification as DC, although in some cases the flow will notnecessarily be a pure DC one as some ripples are likely to be present.

The inverter stage 24 receives the DC power flow generated by therectifier stage 22 and converts it back into AC form. It is beyond thescope of this specification to provide details on how the DC to ACconversion is being performed. This is something known in the art andthe reader is invited to refer to the relevant literature for moreinformation. Generally, the DC to AC conversion is more complicated thanthe AC to DC one, because in the former case the AC wave needs to beoutput with a frequency and phase matching those in the receivingnetwork.

A controller 28 manages the operation of the rectifier/inverter stages22, 24. The controller 28 is computer based, including a machinereadable storage encoded with software for execution by one or moreCPUs. The software defines logic, which determines how therectifier/inverter stages 22, 24 operate. The controller 28 outputscontrol signals 30, directed to the respective rectifier/inverter stages22, 24. The control signals, which can be conveyed wirelessly or overphysical signal pathways, convey commands that control the operation ofcomponents of the rectifier/inverter stages 22, 24.

The controller 28 also receives as input information on the frequency ofthe AC electrical energy in the networks 10 and 12. In particular, afrequency measurement unit 32 supplies frequency information to thecontroller 28 over input signal path 34, which can be wireless orwireline, from the network 10. Similarly, frequency measurement unit 36,supplies the controller 28 with information on the frequency of the ACelectrical energy in network 12, over input signal path 38, which againcan be wireless or wireline.

While FIG. 2 shows the frequency measurement units 32, 34 as beingseparate from the rectifier/inverter stages 22, 24, note that thefrequency measurement units 32, 34 can be physically incorporated in therectifier/inverter stages 22, 24.

FIG. 3 is a flowchart, which illustrates the operation of a single DCchannel of the DC link 14, it being understood that all the DC channelsoperate in the same way.

Assume for the purpose of this example that the electrical energy flowsfrom the network 10 to the network 12. This means that therectifier/inverter stage 22 operates as a rectifier to convert the ACenergy in DC form, while the rectifier/inverter stage operates as aninverter to convert the DC electrical energy into AC form and inject itinto network 12.

At step 40, the controller 28 gets information on the frequency of theAC energy in the source network 10. At step 42, the controller 28determines on the basis of the received frequency information if thefrequency in the source network 10 deviates from the nominal frequencyof the network 10. If a deviation exists, which signals an underfrequency event or an over frequency event, the decision step 42 isanswered in the affirmative and the process continues at step 44.

For more information on the way a deviation of the frequency from thenominal frequency is detected, reference may be made to PCTInternational Publication No. WO 2013/177689 A1.

At step 44 the DC channel 16 provides a response to the frequencydeviation. The response will vary depending on a number of factors, suchas the degree of deviation and the negativeness or the positiveness ofthe deviation, among others. Specific examples are provided below.

In a first scenario, the frequency of the AC electrical energy in thenetwork 10 deviates negatively from the nominal frequency, in otherwords the frequency diminishes. Such deviation is an under frequencyevent, that may result from a power generation deficit. The network 10is thus no longer in a state of balance between power generation andload and the response of the DC channel 16 of the DC link 14 is anattempt to lessen the imbalance by reducing the load on the network 10.The load reduction is performed by diminishing the amount of electricalenergy transferred to the receiving network 12.

Once the controller 28 has determined that the network 10 experiences apower generation deficit, it computes the response based on a responsestrategy. The response strategy, which is encoded in the machinereadable storage of the controller 28, reduces the electrical energytransfer to the receiving network 12 on the basis of the degree of powergeneration deficit. More specifically, the larger the frequencydeviation, the larger the reduction of the electrical energy transferwill be. For instance, the reduction can be proportional to thedeviation of the frequency from the nominal frequency. Alternatively thereduction can be non linear, as discussed again in PCT InternationalPublication No. WO 2013/177689 A1.

In another example of implementation, the controller 28 uses thefrequency information to derive a rate of kinetic energy dissipation innetwork 10. The rate of kinetic energy dissipation is related to therate of variation of the frequency from the nominal frequency, asdiscussed in PCT International Publication No. WO 2013/177689 A1. Thecontroller 28 thus reduces the transfer of electrical energy fromnetwork 10 to network 12 in relation to the determined rate of kineticenergy dissipation.

In terms of the actual implementation of the response by the rectifier;inverter stages 22, 24, the controller 28 sends out control signalswhich regulate the operation of the stages in order to obtain thedesired electrical energy flow between the two networks. For example, toreduce the flow of electrical energy between the networks 10, 12, therectifier stage can be operated such as to rectify only a portion of theincoming AC wave and inject over the DC connections a reduced amount ofelectrical energy. As indicated previously, the rectifier stage is afull-wave rectifier. This means that during normal operation, the wholeof the input waveform is converted to a constant polarity, eitherpositive or negative. When it is desired to choke the electrical powerflow, something less than the whole waveform is converted into constantpolarity. This can be performed by using semiconductor power switchesthat are commanded to block a portion of the incoming waveform. Since afull cycle of the incoming waveform, including a positive half-cycle anda negative half-cycle spans 360 degrees, the semiconductor power switchcan be commanded to block any portion of that 360 degree cycle, thusvarying the RMS DC voltage output by the rectifier stage 22. By loweringthe RMS DC voltage, the amount of electrical energy transferred to thenetwork 12 is effectively reduced.

Another method that can also be used to choke the electrical energytransfer to the network 12 is at the inverter stage 24. Here, thesemiconductor power switches are operated by the controller 28 such asto lower the voltage of the AC output waveform injected in the network12; the lower the voltage, the lower the electrical energy transfer.

It is also possible for the deviation of the frequency from the nominalfrequency to be positive, in other words the frequency increases abovethe nominal frequency. Such an over frequency event is indicative of apower generation surplus; the power and the load are no longer in astate of dynamic balance, rather more electrical energy is beinginjected in the network 10 than what is being consumed.

The appropriate response to an over frequency event is to increase theelectrical energy transfer to the network 12. That transfer can beperformed according to any one of the response strategies discussedearlier, namely linearly varying the electrical energy transfer inrelation to the variation of frequency with relation to the nominalfrequency, in the over frequency domain. Another possibility is to varythe electrical energy transfer in relation to the kinetic energy buildupin the electric generators, namely to reduce that buildup. As indicatedpreviously, the rate of input or output of kinetic energy in the networkis determined on the basis of the rate of frequency variation. Thenotion of “rate of frequency variation” is discussed in PCTInternational Publication No. WO 2013/177689 A1.

A possible variant to the process illustrated in FIG. 2 is to vary thetransfer of electrical energy through the DC link 14 not only on thebasis of the frequency deviation in the source network 10, rather on thebasis of the frequency deviation occurring in the destination network12. In this arrangement, one network assists another when the latterexperiences an under frequency event or an over frequency event.

That variant works essentially along the same lines as the earlierexample with the exception that the controller 28 takes frequencyinformation from the destination network 12 instead of the sourcenetwork 10.

To elaborate, if the frequency information from the destination network12 indicates that a negative deviation exists between the networkfrequency and the nominal frequency, indicating the existence of a powergeneration deficit in the destination network 12, the controller 28operates the rectifier stage 22 and the inverter stage 24 such as toincrease the rate of transfer of electrical energy from the sourcenetwork 10 into the destination network 12. In this fashion, the DC link14 acts to reduce the imbalance in the destination network 12 byinjecting additional electrical energy into it.

In the case of an over frequency event in the destination network 12,the reverse occurs, for instance the controller 28 operates the DC linksuch as to reduce the rate of electrical energy being injected in thedestination network 12, thus lessening the excess generation capacity inthe destination network 12.

FIG. 8 illustrates another embodiment of the invention in which the DClink 100 is provided with accounting control functions to account forthe electricity that is being sent from one network to the other. Theaccounting function is such that it takes into consideration thereduction of the electrical energy transfer occurring during an underfrequency event. The accounting function also takes into considerationthe increase of the electrical energy transfer occurring when the sourcenetwork supports the destination network that experiences an underfrequency condition.

The structure of the DC link is the same as described earlier with theexception of the logging function that describes the various events andconditions that have occurred during the operation of the DC link.During a normal mode of operation, the controller 28 accounts for theamount of electricity that is being transferred from one network to theother, and sends that information over a data link connection to aserver 102. Typically, the server 102 resides remotely from the DC link100. As such, the data link connection is performed through a datanetwork such as the Internet.

The electricity usage data is recorded by the server 102 on amachine-readable storage medium 104. The machine-readable storage medium104 thus stores a succession of records, each record being associatedwith electricity usage occurring over a certain time. In addition tospecifying the amount of electricity transferred from one network to theother, the record also identifies the direction of the transfer and thecircumstances under which the transfer occurred. For example, when therate of electricity transfer was reduced as a result of an underfrequency condition in the source network, the record provides thisinformation since a monetary penalty may then apply to the utilitycompany managing the source network. Similarly, the record would alsospecify when an increase of electrical energy transfer was required tosupport the destination network in which an under frequency conditionexists. That information can be used later on to compute an excess fee,stacking up on the regular electricity transfer fee, to support thereceiving network.

The server 102 runs accounting software that processes the recordsstored in the machine-readable storage 104. The purpose of theaccounting software is to generate debit or credit information as towhat the utility companies, that own the source and the destinationnetworks, owe each other for the transfer of electrical power. Bylogging information on extraneous events occurring during the operationof the DC link 100, such as under frequency events in either network oradjustments to the rate of electrical energy transfer to handle thoseevents, a more accurate debit or credit information can be produced.

FIG. 4 illustrates another embodiment of the invention, which relates toa charger for an electric vehicle (EV). The electric vehicle 46 has abattery 48 that is charged by an EV charger 50. The EV charger issupplied with AC power, which is converted in DC form to charge thebattery 48 of the electric vehicle 46.

Different types of power connections with the vehicle 46 are possible.In the specific example shown in FIG. 4, a wireless connection is usedwhich does not require any physical cable to be connected to the vehicle46 for the battery 48 to be charged. In this example, the EV charger 50has a wall mounted housing 52 from which extends a cable 54 leading to awireless transmission unit 56. The wireless transmission unit 56 has twocomponents; a fixed station 58, and a movable station 60, which ismounted to the vehicle 46. When the vehicle 46 is parked, such that themoveable station 60 registers with the fixed station 58, electricalenergy is transferred by induction between the stations 58 and 60.

The electrical energy received by the station 60 is conveyed to acontroller unit 62 which, in addition to its control functions alsoconverts the AC electrical energy in DC form such that it can besupplied to the battery 48.

In a more traditional form of implementation, not shown in the drawings,the power path to the vehicle 46 includes a physical cable that isplugged in a receptacle on the vehicle's body. To charge the vehicle,the driver needs to plug the cable extending from the wall mountedhousing 52 in the receptacle. Once the vehicle 46 is charged, the cableis unplugged. The wall-mounted unit 52 receives electrical energy in ACform and converts it in DC form such that it is supplied in DC form overthe cable. Accordingly, there is no need to perform any conversationfrom AC to DC at the vehicle.

FIG. 5 is a block diagram illustrating in greater detail the structureof the EV charger 50 and also the controller in the vehicle 46 thatregulates the battery charging process. FIG. 5 applies mostly to thelatter embodiment where a physical power cable is connected to thevehicle 46 for charging it. However, it will be noted that the wirelessvariant works conceptually in a similar fashion.

The EV charger 50 has a controller 64 and a power electronics stage 66.The controller 64 is a computer-based platform with a machine readablestorage encoded with software for execution by one or more CPUs. Thestructure of the software determines the operation of the controller 64.

The power electronics stage 66 performs rectification of the AC waveforminto a DC. As discussed earlier, a full-wave rectifier arrangement canbe used for this purpose. The controller 64 sends control signals to thepower electronics stage 66 over a signal path 68, which can be wirelessor wireline. The signals are used to convey commands to the powerelectronics stage 66 such as to regulate the flow of electrical energyto the vehicle 46, notably by decreasing it in the event of an widerfrequency condition in the network supplying the EV charger 50 withelectrical energy.

The vehicle 46 has an EV controller 70, which is connected to thebattery 48. The EV controller 70 is also software based and one of itsfunctions is to regulate the charging process of the battery 48. Toavoid rapid battery degradation, the battery 48 needs to be charged at acontrolled rate rate. If the battery 48 is completely depleted aninitial rapid charging rate is possible, however that rate needs totaper off when stage of charge of the battery increases, The EVcontroller 70 thus senses the stage of charge (SOC) of the battery anddetermines the charging rate, in other words the rate at whichelectrical energy can be safely injected in the battery.

The EV controller 70 communicates with the EV charger 50 such as toregulate the rate at which electrical energy is supplied by the EVcharger 50. Such communication makes it possible to use the EV charger50 with different electric vehicles that have different chargingrequirements. The communication process allows the EV charger 50 toadapt the charging rate to the specific charging requirements of thevehicle.

The communication can be performed over a physical signaling path, suchas an electrical connector that is integrated into the charging plug,which connects to the vehicle. The signaling path is shown at 72 in FIG.5. The integration of the signaling path into the plug makes it possibleto close simultaneously both the power connections and the signalingconnections once the plug is inserted in the receptacle on the vehicle.

FIG. 5 shows the signaling path transiting through the power electronicsstage 66 to arrive at the charging station controller 64. Thisarrangement is used when the signaling path is integrated into the powercable. Otherwise, the signaling path may bypass the power electronicsstage 66.

A possible variant is to use a wireless communication arrangement, wherethe EV controller 70 communicates with the charging station controller64 by using any suitable wireless communication protocol. Wi-fi,bluetooth and cellular communication protocols are possible examples.

FIG. 6 is a flowchart that illustrates the various steps of the processperformed at the EV charger 50 during the charging process.

At step 74, the charging station controller 64 receives signals from theEV controller 70 that convey to the charging station controller 64charging rate information. It is assumed that the power connection cableincluding the signaling path is connected to the plug at the vehiclesuch that all the power connections and the signaling connections areestablished. In addition to the charging rate information, the EVcontroller 70 and the charging station controller 64 can exchange otherinformation as well, such as when the charging process is to begin (whendelayed charging is desired), identification about the vehicle firbilling/credit purposes, etc.

At step 76, the charging station controller 64 triggers the current flowtoward the vehicle at the desired charging rate. The charging rate canbe determined on the basis of the intensity of the current or thevoltage. The charging station controller 64 thus sends locally controlsignals to the power electronics stage 66 such that it outputs thedesired charging rate. Note that step 74 above is actually a repetitivestep in the sense that the EV controller 70 constantly sends to thecharging station controller 64 a target charging rate. The targetcharging rate changes during the charging process and it is based onfactors such as the achieved degree of charge of the battery and itstemperature, among others. Accordingly, step 76 constantly adjusts thecharging rate based on the target charging rate received from the EVcontroller 70.

At step 78 the charging station controller 64 measures the AC frequencyof the AC power supply and at step 80 determines if an under-frequencyevent occurs. The measurement of the frequency and the assessment ofweather an under frequency condition exists in the power distributionnetwork is performed in the same fashion as discussed in connection withthe previous example and also as discussed in the PCT InternationalPublication No. WO 2013/177689 A1.

If an under frequency condition exists, the charger 50 responds byreducing the electrical consumption of the charger. This reduction canbe made using one of the strategies discussed in connection with theinter-network DC link and also discussed in the PCT InternationalPublication No. WO 2013/177689 A1. The reduction of the electricalconsumption is shown at step 82.

In a possible variant, even if an under-frequency condition is noted toexist, a reduction may not be worth making when the demanded rate ofcharge is low. In such ease, the charger 50 is a minimal load on thenetwork and reducing it further would not yield any substantial benefitin terms of lessening imbalance between power generation and load.Accordingly, it is possible to provide between steps 80 and 82 anotherconditional step that determines the current rate of charging andcompares it to a threshold. If the rate of charging is low and below thethreshold, no action is taken. A reduction of the charging rate occursonly if the current charging demand exceeds the threshold.

Assuming a reduction of the charging rate is desirable, the chargingstation controller 64 proceeds to step 84 at which the charging stationcontroller 64 sends signals to the EV controller to notify the EVcontroller that the demanded charging rate cannot be met. The purpose ofthis signal is to avoid the EV controller 70 to trigger a malfunctioncondition. Since the EV controller 70 is unaware of the reason for thecharging rate reduction, it may interpret the reduction as a malfunctionof the charger 50 and in order to protect the vehicle it will take aprotective action. The protective action may include interrupting thecharging process and also logging an error code via the vehiclediagnostic system.

The downside of triggering a protective action is twofold. First, thecharging process is aborted, such that when the under frequencycondition subsides, the charging does not resume. The vehicle will onlybe partially charged, which is an inconvenience. Second, an error codewill show on the vehicle dash, which is an annoyance since the owner mayhave to clear that may require a mechanic intervention.

However, if the EV controller 70 is made aware that the reduction in thecharging rate is deliberate and temporary, it will not interpret it as amalfunction and will not trigger a protective action.

The way the charger 50 and the EV controller 70 handle the charging ratereduction may vary. One possibility is for the EV controller 70 tocontinue accepting whatever charging rate the charger 50 can offer.Another option is to temporarily terminate the charging process untilthe under frequency condition has subsided. In this instance, thecharging process resumes at a later time.

Resuming the charging process can be done at a specified time; sinceunder frequency events are usually of short duration, typically lessthan 30 minutes, the charging station controller 64 and the EVcontroller 70 may trigger a timer at each end, programmed for a certaintime delay, and once the timers expire, they attempt to re-establish thecharging process.

Alternatively, the EV controller 70 may be programmed to periodicallysend a signal to the charging station controller 64 to query thecharging station controller 64 if it is ready to resume the chargingprocess. While the under frequency condition is underway the chargingstation controller 64 denies the requests; only when the under frequencycondition has passed it accepts the request and the charging processresumes.

Yet another option is for the charging station controller 64 to initiatethe charging process; it sends a signal to the EV controller 70 tonotify the EV controller that it is ready to resume the chargingprocess.

FIG. 7 illustrates the steps of the process implemented at the EVcontroller 70. Some of those steps where described briefly above,however the following description will provide further details.

At step 86, the EV controller 70 determines the charging rate requiredbased on the SOC of the battery and/or other parameters. At step 88, theEV controller 70 sends signals to the charging station controller 64 tonotify the charging station controller of the charging requirements.Steps 86 and 88 correspond to a normal state of operation.

Step 90 is performed when an under frequency condition occurs. The EVcontroller 70 receives the signals from the charging station controller64 indicating that a temporary discrepancy occurs between the commandedcharging rate and the rate being delivered. At step 92, in response tothe signals at step 90, the EV controller 70 refrains from triggering amalfunction condition and any associated protective action.

The reduction of the electrical energy consumption response may thus bemade when various frequency deviation conditions are recognized in thepower distribution network. One of those conditions is a deviation ofthe frequency from a nominal frequency, where what is being tracked isthe difference between the nominal frequency and the instant frequency.Another condition could be the rate of deviation of the frequency, whichrepresents the rate of kinetic energy dissipation in the powerdistribution network. Also, the frequency deviations could be negative(lowering of the frequency) or positive (over frequency). In an overfrequency situation, the reverse response is produced, which is toincrease the electrical consumption. In that scenario, the charger 50notifies the EV controller 70 of the event and of the desire to injectmore electrical energy in the battery. If the EV controller accepts theadditional energy intake, it sends an acknowledgment signal to thecharger 50 that may include also a limit as to how much the electricalenergy injection rate can be increased, to avoid damaging the battery ofthe vehicle.

Certain additional elements that may be needed for operation of someembodiments have not been described or illustrated as they are assumedto be within the purview of those of ordinary skill in the art.Moreover, certain embodiments may be free of, may lack and/or mayfunction without any element that is not specifically disclosed herein.

Any feature of any embodiment discussed herein may be combined with anyfeature of any other embodiment discussed herein in some examples ofimplementation.

Although various embodiments and examples have been presented, this wasfor the purpose of describing, but not limiting, the invention. Variousmodifications and enhancements will become apparent to those of ordinaryskill in the art and are within the scope of the invention, which isdefined by the appended claims.

1. A system for regulating electrical energy transfer over a pathwayincluding a DC link, the system comprising a data processing device,including: a. a machine readable storage encoded with non-transitorysoftware for execution by a CPU, the software being configured forcomputing a rate of electrical energy flow through the DC link at leastin part on a basis of a state of balance between power generation andload in an AC power distribution network to which the pathway connects;b. an output for generating a control signal for adjusting the rate ofelectrical energy flow through the DC link according to the computedrate.
 2. A system as defined in claim 1, wherein the AC powerdistribution network supplies electrical energy flowing through thepathway and the DC link.
 3. A system as defined in claim 2, wherein thedata processing device includes an input for receiving frequencyinformation from the AC power distribution network.
 4. A system asdefined in claim 3, wherein the data processing device adapts thecontrol signal to reduce the rate of electrical energy flow through theDC link when the AC power distribution network manifests a powergeneration deficit.
 5. A system as defined in claim 1, wherein the ACpower distribution network receives the electrical energy flowingthrough the pathway and the DC link.
 6. A system as defined in claim 5,wherein the data processing device includes an input for receivingfrequency information from the AC power distribution network.
 7. Asystem as defined in claim 6, wherein the data processing device adaptsthe control signal to increase the rate of electrical energy flowthrough the DC link when the AC power distribution network manifests apower generation deficit.
 8. A system as defined in claim 3, wherein theAC power distribution network is a first AC power distribution network,the pathway being connected between the first AC power distributionnetwork and a second AC power distribution network.
 9. A system asdefined in claim 8, wherein the input receives frequency informationfrom the first AC power distribution network and from the second ACpower distribution network.
 10. A system as defined in claim 1, whereinthe pathway connects the AC power distribution network to a battery ofan electric vehicle having an electrical vehicle controller, the dataprocessing device being configured to communicate with the electricalvehicle controller.
 11. A system as defined in claim 10, wherein thedata processing device is configured to notify the EV controller that arate of electrical energy flow through the DC link is being diminishedin response to occurrence of a power generation deficit in the AC powergeneration network.
 12. A system as defined in claim 11, wherein thedata processing device is configured to notify the EV controller that arate of electrical energy flow through the DC link is being increasedwhen a balance between power generation and load in the AC powerdistribution network is being re-established.
 13. An electrical vehiclecharger, comprising: a. a power input for connection to an AC powerdistribution network; b. a power output for connection to an electricvehicle to supply electrical energy for charging a battery of theelectric vehicle; c. a data processing device, including: i. a machinereadable storage encoded with non-transitory software for execution by aCPU, the software being configured for determining a rate of electricalenergy flow through the power output by using as a factor a state ofbalance between power generation and load in an AC power distributionnetwork to which the power input connects; ii. an output for generatinga message to a controller of the electrical vehicle to notify thecontroller that the rate of electrical energy flow is being adjusted onthe basis of a loss of balance between power generation and load in theAC power distribution network.
 14. An electrical vehicle charger asdefined in claim 13, including a signaling pathway to transfer themessage to the controller of the electrical vehicle.
 15. An electricalvehicle charger as defined in claim 14, wherein the signaling pathway iswireless.
 16. An electrical vehicle charger as defined in claim 14,wherein the signaling pathway is wire line.
 17. An electrical vehiclecharger as defined in claim 16, wherein the wire line is integrated in apower cable used to connect the electrical vehicle charger to thevehicle.
 18. An electrical vehicle charger, comprising: a. a power inputfor connection to an AC power distribution network; b. a power outputfor connection to an electric vehicle to supply electrical energy forcharging a battery of the electric vehicle; c. a data processing device,including a machine readable storage encoded with non-transitorysoftware for execution by a CPU, the software being configured fordetermining a rate of electrical energy flow through the power output byusing as a factor a state of balance between power generation and loadin an AC power distribution network to which the power input connects;d. the data processing device being configured to negotiate with anelectrical controller of the electric vehicle a rate of charge to besupplied to the electrical vehicle when a loss of balance occurs betweenpower generation and load in the AC power distribution network.
 19. Adevice for controlling a charging rate of a battery, the devicecomprising: a. a first input for receiving information on a state ofcharge of the battery; b. an I/O for: i. sending messages to a chargerto regulate a charging rate of the battery on the basis of the state ofcharge; ii. receive messages from the charger indicative of a loweringof the charging rate unrelated to the state of charge.
 20. A method forregulating electrical energy transfer over a pathway including a DClink, the method including: a. computing a rate of electrical energyflow through the DC link at least in part on a basis of a state ofbalance between power generation and load in an AC power distributionnetwork to which the pathway connects; b. adjusting the rate ofelectrical energy flow through the DC link according to the computedrate.
 21. A method as defined in claim 20, wherein the AC powerdistribution network supplies electrical energy flowing through thepathway and the DC link.
 22. A method as defined in claim 21, includingprocessing frequency information from the AC power distribution networkto determine a state of balance between power generation and load.
 23. Amethod as defined in claim 22, including reducing the rate of electricalenergy through the DC link when the AC power distribution networkmanifests a power generation deficit.
 24. A method as defined in claim20, wherein the AC power distribution network receives the electricalenergy flowing through the pathway and the DC link.
 25. A method asdefined in claim 24, including processing frequency information from theAC power distribution network to determine a state of balance betweenpower generation and load.
 26. A method as defined in claim 25,including increasing the rate of electrical energy through the DC linkWhen the AC power distribution network manifests a power generationdeficit.